(This question is for fantasy worlds like in D&D and other such games.)

Usually, as the adventuring party goes up in ability, they end up facing stronger and more powerful characters. Let's say a party of adventurers comes across the lair of some creatures that would be easy to defeat in combat. These could be orcs or goblins or anything the players could easily overpower. But what if these creatures were very clever, and took plenty of time to defend their home? What would they do?

Let's assume these creatures are more or less human-sized (think goblins, kobolds, orcs, ogres), living above ground in houses or something like that, and with low technology (maybe Neolithic) and no magic.

8 Answers
8

Location.

They will live near a water source, and probably near their fields...

Neolithic hill forts are fairly common. It's a walled village atop an artificial hill, built on the floodplain. It may also have a cistern and/or a well down through the motte/tel. Walls are likely wood, possibly also dry-fit stone for part of the height.

I can tell you from personal experiences in the SCA: Fighting uphill sucks.

Thus, hill forts are an important element of location; when practical, they will be used.

Other variations on location include hillside villages like the Anasazi (and Hopi) used, and inaccessibly high villages like in the Andes, swamp-surrounded villages like old Tenochtitlan, and desert oasis cities all are inherently defended by the trap-like terrain.

Livestock

They will have some livestock in the village at almost all times. Not all of it, but easily a weeks worth of food.

The rest of the livestock is generally close to the village...

Remember:

Cows, espeically in numbers, can be dangerous in their own right. Especially with persons they don't recognize. That means the PC's.

Sheep, pigs, and goats can be downright nasty fighters and quite territorial, in addition to typically being present in significant numbers when present. And a single unhappy sheep or goat is a danger; and unhappy pig is a lethal trap in its own right.

Troop positions

Archery and/or slinger positions on the walls. The raged weapon guys firing down get extra range and damage out of the deal, making fighting uphill suck even more.

In societies with a single handedness dominant, the accessways will be configured for that handedness to swing against those entering, but to impede swings by those who are entering.

Absent things

What they won't have is long-standing traps away from the gate and/or just outside the walls. It's too much a problem for the locals. They also won't have much in the way of mechanical traps. Maybe a swing-log¹ into the gate area, just to beat the snot out of the guys trying to batter the gate down, but that's able to be kept pretty safe, and doubles as a bar on the door.

They also won't have pit traps anywhere near livestock. Too much risk.

Any traps they do set will most likely be temporary, and manually operated. Snares as temporary traps, sure, but only when the cattle, sheep, pigs, goats, and rabbits are contained, or in areas those won't go.

¹: Best exemplified by some ewok traps in SW:ROTJ.
²: I watched a guy dragged off to the hospital by the police when he attempted to break into a friend's home, which had a goose resident. Goose broke both his arms, both his legs, and half his ribs. Oh, and Goose, swans and loons will all imprint on just about all the yard animals, and so if you attack any animal they think of as "family" they will defend that critter.

Fantastic answer. But one thing left out, sometimes the best defense is a good egress. Hunter/gatherers (most neolithic were...) are set to move the entire camp on little notice and even permenant settlements would be abandoned quickly if an overwhelming force was coming. If a bunch of low level creatures know a big threat is coming, they might not be there when it arrives. Similarly, the warriors might stay to delay while the others flee, with the best loot...forcing the PCs into a chase if they want a total defeat and the best loot.
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TimothyAWisemanMar 20 '12 at 19:44

Most of the advantage people/creatures have when setting up low tech defensive works tends to be environmental/situational. Unless in time of war, generally it's safety first though, and low cost - you don't have a pot of boiling oil or black pudding lying around for someone to trip over.

Besides @aramis' great suggestions, I'd tend to say once you get into their "houses" you have to deal with a lot of preplanning - they will have thought about, for example, that if they sit just there, they'll get to shoot at the lower body of someone coming through their door without being immediately seen. Expect a lot of not seeing them the first round or them being in a position that takes a couple rounds to get to while exposing yourself to attack. Narrow squeezes, half height doors, and improvised difficult terrain as well. Many will keep dogs or other relevant mean animals around as well, for warning as well as combat.

Now, if you are positing a more "high combat" environment and not just a normal ville kind of thing, then you get stuff like Tucker's Kobolds, where you can certainly contrive even low hit point opponents having "extreme" trap and tactic combinations.

Although even the more low tech guys will get more creative if they know the PCs are coming (via scouts, or survivors from nearby torched hamlets). Then, you might expect them to have pre-corralled the kids and livestock and gone all Viet Cong on them - low pits with pungi stakes, closed the gate and maybe put spike hedges behind it, readied missile weapons... Only if truly desperate would they resort to fire or whatnot though, as that tends to burn down their ville as well as the PCs would.

If they have more than a little bit of warning, then they'd seek help from nearby settlements, any larger government/lord, or maybe scraped together some gold and wenches to get the orc equivalent of an adventuring party to try to kill the PCs (ideally away from the village...).

One thing that would work strongly in their favor is traps which are designed to separate the party. For example, a hidden portcullis that drops down after the first party member passes a spot. Or perhaps a random teleport trap that teleports each party member to a different location (though that's likely beyond a group of orcs or goblins). As my paladin once found against a group of bugbears when he got separated from the party, a single PC is much easier for a group of monsters to pick off.

Another option is that the monsters hire themselves out to a more powerful creature or NPC, thus gaining the protection of that more powerful foe in return for their service.

Another option I've seen work well is hit and run tactics from hidden spots. Wear down the party over time and make them use up HP and healing while suffering little in the way of losses themselves. Well executed it can be done in any terrain or location, especially if it's designed to give them plenty of places to hide and attack from as well as quick avenues of escape that the PC's can't easily follow.

A motte and bailey castle maybe appropriate. A strong patron (say a dragon) could be another good protection. A side note: If they have authorisation and protection from the local lord, attacking will brand the characters as criminals (serial killers?). Finally, they could always hire seven warriors to protect them while danger is about.

Mostly, what are they protecting against? Large armies? Brigands? Blood thirsty genocide bend characters? The strategies will depend on those. But keep in mind one thing: the more secure something is, the less easy it is to live there. If the place was so dangerous, why not just move or kill the danger?

IF Defense Fails Pull Troops Back & Use War BEASTS In Side OF Town. Delay of Boss Beast. Fearing to release the "Worst of the Worst" captured War Beast last moment. Hold back smaller poisoning beasts, to kill off their Boss monsters "Worst of the worst".

Walls: 3 outer wall layers, Fortress or Picket thick, middle wall made like Log Cabin log pile. Defenders Topple on Attackers To Make Stampede More Dangerous. Release Fearful enraged LARGE Planned Cattle Monster Trample Stampede! Between First AND Second Walls.
DEATH BY BY Hoof and Crushed under Living Kicking Stomping Life MASS.

Allies Possible More "Enlightened" Human barbarians and savages Who no Hate Other Non Humans. In alliance or live as Ville allies, Chaotic Neutral.

Children Make GREAT Trap Setters Younge teen or younger Adolescence Work Hard to Honor parents, And will Invent and do Things wrongful to their own cultures War and Civil morals CREATIVELY. Farm Boys ;) crawl into small holes & Trip lines by Beast pull labor strong mammals/lizards pets. Throw Poisoned thorn trip Bola weapons!

Teaching Jokes. Catch and release! Parents are very thoughtful teachers!

Drace, this is a great edit but some more work could be done. As it is, it's not that easy to read. Take some time and correct the one or two spelling errors, and expand some of your points into full sentences.
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PureferretMar 20 '12 at 19:53

While this still lacks in clarity it's a significant improvement. I've reversed my vote as the ideas are good here. One thing I will suggest is actually registering your account so that you can keep your rep even if you lose your cookie.
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wax eagleMar 22 '12 at 12:32

I would firstly base what they'd do on their Intelligence -- a low Intelligence creature might not do much beyond simple concealment and crude traps. Plus, some are social creatures -- so a lair's defense might be sheer numbers.

However, more intelligent creatures might be pulling of Grimtooth's Traps level defenses on you (some of which could be subtilely lethal [magically or non-magically])
(On a side look at Grimtooth's Dungeon of Doom)

@Joe:Grimtooth's Traps are a series of 4 books plus the Dungeon of Doom which describe a whole series of traps ranging from simple (and sometimes less lethal) to very complex (and very lethal). Some are mechanical and some are magical. Dungeon of Doom is an entire dungeon of these traps strung together.
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David FassDec 3 '14 at 3:02

Something you have to look at: How much effort is the creature able to expend on such protections. The best defense is to not fight in the first place--say, a fake lair.

The clever monster living in that cave? Remember that big chamber with all the stalactites you passed through to get there? His real lair entrance is up there where it is completely invisible from the ground. What you found that looks like a lair but with the bad luck of him being out when you came knocking was really a decoy. (He has some sort of levitation item or ability to get in and out.) Since it's actually a decoy he's not so limited in what he can do with traps.

Remember that stream you crossed on the way in? The entrance is actually under that fallen log.

That body in the vampire's coffin is just an ordinary body that the vampire staked. His real coffin is behind that wall that no dwarf would admit to having constructed. (The stones don't fit tightly enough, the vampire can get through in gaseous form.)